1. Field of the Invention
This invention relates generally to optical disk reproducing apparatus, and more particularly is directed to optical disk reproducing apparatus or players for so-called compact disks having both audio and video signals recorded thereon and which are generally referred to as CDVs.
2. Description of the Prior Art
Various TV color systems, such as, the NTSC and PAL systems, are employed as recording formats for video disks, and these recording formats are similar to the correspondingly designated standard TV broadcasting systems. These standard TV broadcasting systems differ somewhat from each other. For example, an NTSC video signal has a frame frequency of 30 Hz and 525 horizontal scanning lines in each frame, while a PAL video signal has a frame frequency of 25 Hz and 625 horizontal scanning lines in each frame.
When a video disk recorded with a video signal according to the PAL system is employed in a video disk player or reproducing apparatus designed for use with an NTSC video disk, that is, a video disk recorded with a video signal according to the NTSC system, the fact that the difference between the frame frequencies of the PAL and NTSC video signals does not exceed 20% of the frame frequency of the NTSC signal makes it possible to achieve locking of the disk rotation servo with the result that an unsatisfactory video signal is obtained at the output of the video disk player. When such unsatisfactory reproduced video signal is supplied to a monitor, the latter displays a slightly disturbed black-and-white picture which is devoid of color even though a color video signal is recorded on the disk being reproduced. The display of such a defective picture on the monitor is frequently misunderstood by the user who believes it is the result of a defect or misoperation of the video disk player, rather than merely the result of seeking to playback or reproduce a video disk recorded with color video information according to one TV system by means of a video disk player intended for use with video disks recorded with color video information according to another TV system. By reason of the foregoing, the manufacturers or other sources of optical video disk players are frequently the object of unnecessary complaints or so-called nuisance calls from unjustifiably irate users of such apparatus.
In order to avoid the foregoing problem, it has been proposed to provide an optical video disk player with a device for identifying whether an optical video disk being reproduced has been recorded with color video signals according to the PAL or NTSC system by detecting and counting synchronizing signals contained in the reproduced video signal. Thus, for example, the number of horizontal synchronizing signals between successive vertical synchronizing signals, which number is different for the PAL and NTSC systems, may be counted for identifying whether the optical video disk being reproduced has been recorded according to the PAL or the NTSC system. However, a rather complicated circuit arrangement, including a counter circuit, is required for identifying the TV system used for recording the optical video disk in the described manner. Further, when the TV system used in recording the optical video disk is inconsistent with the TV system for which the optical video disk player is intended, the signal reproduced by the player is unstable with the result that the synchronizing signals included therein cannot be reliably detected. Therefore, there is some risk that the PAL, NTSC or other system with which the optical video disk has been recorded will not be reliably identified.
Recently, a so-called CDV has been developed as an outgrowth of the now widely used compact disks or CDs. A CDV is an optical disk of the same size as a CD, but with only audio signals being recorded in a radially inner track area of the disk, while video signals are recorded in a radially outer track area of the disk. In the CDV, the video signals recorded in the radially outer track area can be in accordance with the PAL, NTSC or other color TV system, while the recording format for the audio signals recorded in the radially inner track area is the same as that used for CDs, and thus is according to a world-wide standard which is independent of the TV broadcasting systems varying from country to country. Thus, when a CDV is reproduced on a CDV player, the audio or music programs recorded on the CDV in accordance with the standard format can be consistently reproduced correctly even though the video signals recorded in the radially outer track area of the CDV are in accordance with a TV system that is different from the TV system for which the CDV player is intended. As a result of the foregoing, an operator of a CDV player who has successfully reproduced the audio or music programs on a CDV is likely to believe that the CDV player is defective or at fault when an attempt to reproduce the video programs on the same CDV leads to a disturbed black-and-white picture devoid of color. Therefore, misinterpretation of the cause of the defective or unsatisfactory video playback by the CDV player occurs frequently, and the problem of unjustified complaints or nuisance calls to the manufacturer or other source of the player has become increasingly serious.